About.com: The Magic SysRq KeyDec 02, 2000, 18:08 (16 Talkback[s])
(Other stories by Aron Hsiao)
"When compiling your own Linux kernel, have you ever wondered just what the last option having to do with the "Magic SysRq Key" is? As luck would have it, this is one of the most useful options a small Linux system can enable."
"Linux is stable, but let's face it -- there's a lot of beta-quality hardware and software out there. Sometimes things just lock up, and then you're forced to hit reset, wait for fsck to do its thing, and potentially even lose data because you didn't get a chance to sync before restarting. This is where the magic SysRq key comes in. When enabled, it provides a set of "emergency" options which will usually work even when the rest of the system (even X) seems to be locked up hard. With this option enabled, the following keystrokes will be available at all times..."
"These keystrokes won't work all the time -- there are rare occasions when the kernel itself is just completely frozen, usually due to hardware error or running experimental kernels -- but these keystrokes work consistently enough to be a major help, especially if you're doing something (like X software development) which has a habit of freezing your console."